Field of the Invention
This invention relates to stepping motor systems, particularly to stepping motor drivers, and more particularly to driver compensator circuits that permit the driver to inhibit the rotor instability that occurs when the driver applies pulses to a stepping motor over a range of mid-frequencies, such as from 300 to 40,000 steps/sec.
Stepping motor systems, and their operation, are well known. Typically, a motor driver responds to a stream of command pulses and applies step pulses to coils on the motor's stator. A number of circumferentially-distributed inwardly-extending stator teeth magnetically drive circumferentially-distributed outwardly-extending teeth on the motor's coaxial rotor. Each driver pulse steps the rotor relative to the stator so that the pulse frequency, at least partially, establishes the motor speed. The motor speed corresponding to the pulse frequency of the input command pulses is referred to as the input command pulse speed.
Mid-frequency stepping motor speed instability, or reduction of velocity damping, is a condition which is inherent in any conventional stepping motor system, and is due to the influence of the internally generated motor back-EMF on the motor current. It causes destabilizing side band components to oscillate the rotor about the input commanded speed. A variety of active feedback techniques have been employed in the past to control mid-frequency instability. Each of these prior techniques involved significant added driver complexity, and imposed undesirable performance limitations.
An object of the invention is to improve stepping motor systems, and/or drives.
Another object of the invention is to provide a stepping motor drive, or compensator circuit for a drive, that inhibits mid-frequency instability.
Still another object of the invention is to overcome the limitations of prior stepping motor systems and drivers.